


Equal Exchange

by Maireeeee



Category: Teenage Mutant Ninja Turtles (TV 2012)
Genre: Angst, Dysfunctional Family, Episode AU: s03e18 The Deadly Venom, Episode Tag: s03e18 The Deadly Venom, Family, Family Feels, Gen, Hurt/Comfort, Leo-centric - Freeform, Ninja Healing Hands™️, Not Beta Read, bc come on, isnt the healing mantra a little too convenient, overprotective!brothers, poor Leo, sick!leo, will add more tags later on
Language: English
Status: Completed
Published: 2019-06-21
Updated: 2019-06-21
Packaged: 2020-05-15 23:27:53
Rating: Not Rated
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 2,902
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19306033
Author URL: https://archiveofourown.org/users/Maireeeee/pseuds/Maireeeee
Summary: “This particular variation of the mantra drew on my energy reserves from other parts of my body, allowing me to channel it to my knee. In the midst of battle, it can be used to draw on the user’s deepest, untapped energy reserves to grant a few extra minutes of strength in battle. And as you know, a few minutes of strength can be crucial to victory- or can buy you enough time to retreat.” Splinter gazed keenly into his son’s blue eyes, ensuring Leo understood what he was saying. “But afterwards, even the strongest and most experienced Master would feel drain and fatigue.”..Or, the Author refuses to believe that a mystical cure-all doesn’t come without some kind of trade-off. AU of s03e18: The Deadly Venom.





	Equal Exchange

**Author's Note:**

> So, in all the fandoms I’ve been a apart of, there is NEVER such a thing as a convenient miracle cure-all that doesn’t have some sort of negative trade-off on its user.   
> That being said, you can’t convince me that an all-encompassing healing mantra just conveniently heals all illnesses without any backlash onto the user- or no doubt Splinter would have used it a lot earlier, and it would make Donnie’s doctor skills kinda moot.
> 
> So, my take on it:
> 
>  
> 
> P.S. btw disclaimer, I dont own TMNT or else we wouldn’t have just five seasons. Also, haven’t watched past season 3 yet, so not canon compliant probably.

_“However, Leonardo- do not use this technique so lightly,” Splinter warned sternly as he and his eldest rested their hands on their knees. His younger sons had retreated from the door of the dojo to prepare dinner, but Splinter had kept his blue-clad son from following immediately._

 

_“The healing mantra has several variations for various purposes, but remember that all it does is redirects and channels the user’s energy flow- it is not a miracle cure. All I have done now is relieve the pain in my knee, for a certain amount of time.” Gingerly, the elderly rat began to shift his weight, preparing to raise himself up off the floor. Immediately, Leonardo moved to help him, acting as support for his father to use to stand. “This particular variation of the mantra drew on my energy reserves from other parts of my body, allowing me to channel it to my knee. In the midst of battle, it can be used to draw on the user’s deepest, untapped energy reserves to grant a few extra minutes of strength in battle. And as you know, a few minutes of strength can be crucial to victory- or can buy you enough time to retreat.” Splinter gazed keenly into his son’s blue eyes, ensuring Leo understood what he was saying. “But afterwards, even the strongest and most experienced Master would feel drain and fatigue.”_

 

_“So, it’s like borrowing energy ahead of time,” Leonardo mused, and Splinter felt a stab of pride at how quickly his son had grasped the concept._

 

_“Precisely. When used on oneself, in this situation. On another person, it is a completely different matter;_

 

_“When using the healing mantra on another person, you deplete your own energy stores in order to restore theirs. In return, you also experience their pain and fatigue, though you do not have the wound to match it. However, in extreme cases, the pain alone has been enough to render the user incapable of participating in battle.”_

 

_“So it’s like an exchange,” Leo mused. Splinter nodded. “Precisely. This kind of healing does not come without a price, my son. It is not something one can use just whenever. And I know you, Leonardo.” Splinter’s eyes narrowed as he placed his hands on his son’s shoulders. “You are a brave and strong leader, one who cares much about his team- his brothers. And you have proven, time and again, that if you can protect them, if you can spare them any harm, you would._

 

_“But please, my son, do not take this to an extent that you may not recover from.” The rat that was once Hamato Yoshi closed his eyes briefly, thinking to a cloudy, cold afternoon, and a lone katana abandoned in an industrial building site. “Twice, I have nearly lost you, Leonardo- first when you bought time for your brothers and April to escape from the Kraang ship, and again just months ago, when you faced the Shredder alone and slipped into a three-month coma. Your brothers and I could not bear to lose you again.”_

 

_Leo’s gaze dropped. “Hai, sensei. I promise.” Steel blue eyes met Splinter’s gaze. “As long as my interference is not necessary, I won’t use this technique.”_

 

_Splinter sighed, weary. The lesson of sacrifice was a necessary one for any leader to learn, but there were times he felt that it was a lesson his eldest had learned too well._

 

_Leonardo noticed the sudden droop in his father’s posture. “Come on, sensei. It looks like you’re feeling the drain already. Maybe you should rest first, I’ll get Mikey to take you some food and tea in your room.”_

 

_“Thank you, Leonardo,” Splinter smiled. “But I will rest after dinner. The Kraang and the Shredder have already stolen months of time with you and your brothers away from me. I have learned to cherish every opportunity to spend time together where you are not at each others’ throats.”_

 

_As if on cue, there was a clatter of metal and ceramic from the kitchen, along with raised voices. Splinter sighed. “Perhaps I spoke too soon.” Nonetheless, he smiled as he allowed Leo to help him out of the dojo towards his other sons._

 

* * *

**__**

Leo fought the wave of darkness threatening to crash over him as the Foot soldiers carried his weakened body over the train tracks. In the background, he heard Karai speaking, but Leo was too busy trying to fight the waves of nausea and pain rolling over his body.

 

The sound of chains alerted Leo to the fact that they were probably going to string them up- Karai’s venom had already been taking effect earlier, messing with his vision, but he’d still seen the way Casey, Mikey and Raph had been chained up and hung like trophies- or bait. He couldn’t let that happen to him too, or else there was no way that he and his brothers could escape- and then Master Splinter would have to come out too. And they couldn’t afford that, not with Master Splinter still recovering from Slash’s attacks and April poisoned-

 

Some part of Leo clenched in horror and despair as it registered that it was probably Karai who had poisoned April, that he and his brothers had been infected with the same venom, and that even Donnie, their genius brother, had been unable to find a cure.

 

Unless Leo did something, now, they were all going to die.

 

“Rin.”

 

‘ _Do not use this technique so lightly.’_

 

“Pyo.”

 

‘ _The healing mantra redirects and channels the user’s energy flow.’_

 

“Tou.”

 

_‘Enough to buy a few extra minutes of strength in battle- which can be crucial to victory,_ ’

 

“Shah.”

 

‘ _Or to buy you enough time to retreat.’_

 

 

The Foot ninjas dropped them on the floor- Karai’s voice got louder as she drew nearer.

 

“Rin. Pyo. Tou. Shah.” Undirected, he could feel the energy coursing haphazardly through his body. It was enough for him to regain control over his limbs and grasp one of his daggers.

 

“- and then, I will have my revenge,” Karai was still speaking, and Leo took advantage of a sudden surge of strength to jump to his feet, simultaneously taking out the ninja surrounding him and dropping Donnie on the last one. He grunted, already weary. He was dangerously aware of how rapidly Karai’s venom was working.

 

“Beating the poison- impressive,” Karai’s voice was cooly distant, amused even. A snake, toying with its prey.

 

“Shredder... used some kind of brain worm on you,” Leo pleaded. After everything- he had to believe he could reach Karai. How he felt for her was complicated now- yes, he’d liked her (and still did to an extent) but she was also _Miwa_ \- Master Splinter’s daughter, who he’d thought dead for almost two decades. That also made her his sister- and there was nothing that Leo wouldn’t do for his siblings.

 

“Lies won’t help you, Leo,” Karai said coldly. “I’ll just finish you myself!”

 

Shouting a battle cry, Karai lunged, sprinting towards him. Leo had fought Karai before- he knew she was wicked fast, and that had been _before_ she’d become a snake mutant. Add in to the fact that her venom was still affecting him, slowing his reflexes- it was all Leo could do to shift his stance into a ready position, forcing back the echoes of numbness and pain.

 

His eyes tracked Karai’s movements as she leaped from the tracks, using the platform as a jumping board to kick at his head. He barely managed to block and dodge her blows and kicks as he gave ground, still trying to reach past the brain-worm’s influence and appeal to the girl he’d befriended (who’d betrayed him, who’d covered for him, then betrayed him again- they had a very complicated relationship, okay?)

 

“You have to fight it!”

 

Karai only gave a wordless cry, lunging as her arms morphed into snakeheads, forcing Leo to try and dodge, only for the snakes to wrap around his arms and neck before Karai threw him through the air.

 

Leo couldn’t help his cries of pain as he landed on the tracks again, rolling and bouncing from the force behind Karai’s throw before sliding to a stop.

 

Every movement he made as he stood sent his muscles aching and burning in protest. The mantra had slowed the poison, definitely. But he was already feeling the fatigue that Splinter had warned him of earlier. As it was, his reflexes were sluggish, slow- and he could only stare in horror as Karai’s snakes latched their fangs deep into his arms and pulled him straight into the path of Karai’s next attack.

 

He flew backwards again, into a pillar before collapsing on his knees. Dimly, he registered that Karai was still approaching. “Still feeling the effects?” She taunted.

 

Leo’s arms were on fire. He could feel the pain radiating out from the puncture wounds on his upper arms as he struggled to stand.

 

“You’re weak, Leo. And you’re done for!”

 

* * *

 

_“Master?”_

_Splinter looked up at the blue-masked turtle. The two of them were alone once more, this time in the kitchen. Leo’s brothers had left, declining Leo’s offer of tea, Raph and Mikey to the pit and Donnie to his lab. “Yes, Leonardo?”_

_“You said there were other variations of the healing mantra? What for?”_

_Splinter set his cup down, stroking his beard. “The one I have taught you, as I said, redirects energy for a temporary period of time. It stabilized my knee and blocked the pain from my mind, but it has not healed it. Other variations can heal wounds, cure illnesses, but it is much more dangerous. It takes a lot more energy than simply negating the pain one is experiencing in order to completely heal a wound. In some cases, it can even be lethal.”_

_Leo looked down at his hands. At first, the idea of being able to heal his brothers and friends so easily had sounded cool, but now..._

_“I trust you with this knowledge, Leonardo, because I know you are wise enough to know how and when to use it. The lessons of sacrifice, responsibility, and leadership are ones you have learned well.” Splinter sighed. “I only pray, my son, that the time you will use it is not nigh.”_

* * *

Leo glared at Karai, and beyond her, to his brothers and Casey. His limbs burned and ached, his eyes watered and his head throbbed, but he knew that if he didn’t do this, then his brothers were as good as dead- and after them, their father. And he couldn’t allow that.

_Only when absolutely necessary, sensei._

_“ **Rin. Pyo. Tou.”**_

_Casey. April. Donnie._

_“ **Shah. Kai. Jin.”**_

_Mikey. Raph. Karai._

_“ **Retsu. Sai.”**_

_Master Splinter._

_“ **Zen**.”_

_Father._

 

* * *

 

When they got back to the dojo, Leo was thrilled to see April up and about, though he saw the droop in his father’s posture. He was tired. It looked like he wasn’t the only one who’d had to perform the healing mantra recently.

 

Master Splinter looked relieved, if concerned, to see all his sons plus one Casey Jones return home, and when Leo had explained that his brothers had also been subjected to the same kind of venom April had been exposed to, they’d laid the unconscious boy and turtles out in the dojo.

 

So far, Leo hadn’t experienced the exhaustion his father had warned him about. Still, he’d decided to leave out having to perform the mantra on himself multiple times lest Splinter take on the task of healing all four of their patients on his own.

 

He’d just mention it after. Yeah. Sure. Let’s go with that.

 

Thankfully, the mantra and technique for poison was relatively easy, and apparently not as life-threatening as actually curing an illness or healing a wound. The way Master Splinter described it, poisons were like guerilla ambush attacks upon an army. They only held the advantage because they’d taken the body’s immune system by surprise. The healing mantra to take care of poison simply contained the poison and jumpstarted the immune system into working again. “Once the body regroups enough to overcome the poison, it does not need much more help.” It was only because April had already been at the latter stages of the venom’s effects that Master Splinter had needed to interfere further.

 

Leo looked over his brothers. They looked groggy and tired, but otherwise alright, especially Mikey.As they started talking about Karai, though, Leo felt a wave of exhaustion wash over him. Suddenly, he was very, very tired of the whole affair, and silently, he retreated from the dojo.

 

Shell, he felt _so_ drained. His eyelids felt heavy, his limbs were numb, and he felt like the slightest gust of wind could have bowled him over. Beyond that, though, he felt guilty that once again, he hadn’t been able to bring Karai home. Logically, he knew there was nothing more he could have done for her, not with the brain worm still controlling her and his brothers down. But logic had never much factored in when Karai was concerned. From the moment he’d met her, she had thrown off Leo’s logic, moral compass, even his loyalty to his brothers- something he’d thought uncompromisable. And true, he’d grown since then, but Leo could no longer trust himself or his decisions when Karai was involved.

 

“You should be celebrating your victory.”

 

Leo started, surprised that Master Splinter had managed to sneak up on him. Although his sensei _was_ a ninja master, it had been ages since he’d been able to completely surprise Leo- particularly now that he was using his cane. “You did a great thing tonight, Leonardo. You saved everyone.”

 

Guilt struck him as he thought of the lost, shaken look in Karai’s eyes when he’d recovered and struck back. For a moment there- he’d thought he’d gotten through to her. Then she’d disappeared. “Not everyone,” he replied bitterly, unable to meet his father’s eyes, afraid of any judgement he might find.

 

“I tried to get Karai out of Shredder’s control. I _failed_ , Sensei. I’m sorry.”

 

Leo didn’t realy know what he expected Master Splinter to reply- rarely did his father actually get angry at them, but somehow, Leo felt his disappointment was much worse. But somehow, Leo hadn’t anticipated the warm understanding- and pride?- in his father’s voice. “We saved her once, Leonardo. Perhpas, we can save her again. And now, you show great gifts as a healer. Being at the edge of your life gave you a power that few martial artists can tap.

 

“I am proud of you, my son.”

 

Leo took a moment to let that sink in? Proud of him? Even after he’d let Karai get away? Even though his brothers had still gotten poisoned, had suffered because of him?

 

Out of the corner of his eye, he noticed his brothers exchange glances and slip out of the dojo. Donnie went first, smiling sheepishly.

 

“Um, Leo... we just wanted to thank you- for saving us.” There was warmth, and even awe in Donnie’s expression as he smiled at Leo, and it was mirrored in Mikey and even Raph’s faces. Leo’s chest expanded with emotion at the sight- it felt like ages since he’d last seen his brothers look at him that way.

 

“Yeah!” Raph’s voice was breathily excited, almost like it used to be when they were children and Leo had managed to pull off a move flawlessly, before everything had been a competition between them. “You kicked Footbot butt, stopped the poison, got us out of there, and you did it solo! None of us could’ve done that!”

 

And maybe it was just because he was freaking exhausted, and being surrounded by his family with Casey and April and her father, but Leo couldn’t bring himself to argue with his brother’s grins and his father’s proud smile as he pushed Karai to the back of his mind.

 

“Maybe you’re right.” He turned to his father, smiling weakly. “Maybe today was a win.”

 

* * *

 

 

Later, while Mikey and Raph battled it out for the last slice of pizza, Leo took advantage of the general chaos to slip out of the kitchen and escape to his room. The exhaustion that had lingered on the edges of his mind earlier had now seeped into his very bones and he just wanted to sleep.

 

His mind wandered back to Karai and how confused and conflicted she’d seemed when he’d finally managed to overcome her venom, enhancing his strikes with the mantra in an attempt to drive the brain-worm’s influence from her mind. He’d only just learned the mantra, and wasn’t completely sure how it worked but it had been worth a shot.

 

For a moment, he’d thought it actually worked.

 

It barely registered to Leo that he’d been stumbling, his feet dragging over the cold tile as he approached his room. His hand didn’t seem to want to cooperate as he reached for the doorknob, and his legs somehow ran into one another, sending him toppling to the floor. Leo’s vision blurred, and he blinked, confused that the doorknob he’d been reaching for had somehow moved so far away.

 

Distantly, he heard his father and brothers’ voices raise in alarm, but his eyelids were already drooping. There were hands on his shell, his limbs, under his head, tapping his cheeks, but Leo couldn’t bring himself to open his eyes. He was just... so... tired...

 

 

 

**Author's Note:**

> Reviews are loved! Or hit the kudos button below.
> 
> I have no real updating schedule, so expect my updates to be sporadic, at best.


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